Hi,
Just expanding the menu on load is as simple as using the following (after the menu is initialized):
$('#main-menu').smartmenus('itemActivate', $('#main-menu a.current').eq(-1));
But I suspect you probably would like the menu to behave a bit differently than the others. For example, hide it when some other sub menu is shown but show it again automatically after the other one is hidden (i.e. make it sort of sticky). So if you need further tweaks, please explain in details how exactly it should work and also it would help very much if you could post a live example so I could test your exact code.
Cheers!
